Functional studies of two cloned non-allelic human methionine initiatior tRNA genes were continued. Both tRNAimet genes were mapped in the human karyotype on the short arm of chromosome 6. The previous discovery of the transport defect of the variant human tRNAimet has been extended, resulting in the discovery of a carrier-mediated translocation mechanism utilized in the transport of tRNA species from the cell nucleus. The enzymes which process the primary transcript of the human tRNAimet gene have been purified from X. laevis ovaries. The 5 feet processing enzyme appears to be an RNase-P like activity, physically associated with an abundant intranuclear small RNA and functions as an endonuclease. The 3 feet nuclease is a separate enzyme, active only on the primary transcript after 5 feet processing. The 3 feet nuclease is a multisubunit enzyme capable of autophosphorylation. We have discovered that the basic processing-transport pathway utilized in tRNA biosynthesis appears to be strikingly similar to that of another class of small RNAs, the alu sequence, as judged from our studies of such a sequence contained in the mouse alpha-fetoprotein gene.